Hydraulic punching machine



mvenrbn:

Franci 5 J. CLOUP ATTORN BY F. J- CLOUP HYDRAULIC PUNCHING MACHINE 2Sheets-Sheet 1 7 J 1 Q N w 2 W Sept. 30, 1969 Filed Dec. 12, 1966 Sept.30, 1969 F. J. CLOUP 3,469,481

HYDRAULIC PUNCHING MACHINE Filed Dem-12. 1966 2 Sheets-Sheet B HgZINVENTOR Francis J. CLOUP ATTORNEY United States Patent Int. Cl. iszsr1/14 US. Cl. 83140 2 Claims ABSTRACT OF THE DISCLOSURE A hydraulicpunching machine for punching metal sheets in which knocks and shocksproduced by punching are automatically eliminated. This is achieved in ahydraulic punching machine in which the upper face of the hydraulicpiston is subjected to a high hydraulic pressure by supplying meanswhich apply a permanent damping fluid pressure to the lower face of thepiston, said damping pressure being lower than the high pressure whichis applied to the upper face of the piston. The means for applying thispermanent pressure includes a modification of the fluid chamber of themachine. The damping pressure fluid penetrates into said chamber whichcontains the lower part of the piston through an opening having a crosssection small enough to cause the necessary pressure loss between theupper face and the lower face of the piston.

The present invention relates to a high-power hydraulic punching machinethat does not give any knocks or shocks upon clearance.

It is known that hydraulic punching machines produce knocks and shockswhen the punch goes through the part to be punched. These knocks andshocks are due to the rapid cancellation of the elastic energy in thecontrol hydraulic fluid located in the punching machine piston chamber.

According to the invention, these knocks and shocks are eliminated byapplying, on a permanent basis a damping hydraulic fluid underintermediate pressure on the lower surface of the piston, this hydraulicfluid penetrating, in addition, into said chamber through a smallsection opening in such a manner that this intermediate pressure and theoverpressure, due to pressure loss through this opening, balances thestress and energy available on the piston after punching or shearing ofthe iron sheet.

The invention will now be described in detail in relation to theattached drawings in which:

FIGS. 1 and 2 respectively show the punching machine of the inventionand the punching machine separating unit; and

FIG. 3 shows this punching machine control hydraulic circuit.

Referring to FIG. 1, 25 designates, as a whole, a high power, forexample 30 ton, punching machine, capable of punching holes 26 mm. indiameter into /2-inch mild steel.

The punching machine comprises a hollow body 1 fixed to a base 2 and amobile piston 3 in the chamber of this body. 4 denotes the upper chamberabove the piston and 5 the lower chamber below the piston. The drivinghydraulic fluid is brought into the axis of the upper chamber 4 throughpipe 6 under a pressure of the order of 3,500 p.s.i. and the dampinghydraulic fluid is brought laterally into the lower chamber through pipe7 and junction 8 under a pressure of the order of 700 p.s.i.Communication between lower chamber 5 and inlet channel 9 of the dampingfluid occurs through a restricted passage 10. The size of this throttlepassage is set so that the pressure loss due to the restriction togetherwith the 3,469,481. Patented Sept. 30, 1969 intermediate pressure issufficient to balance the high pressure of the driving fluid at the timewhere punching goes throughout.

The punch-bearing spindle 11 which is in the form of a hollow rod isscrewed into piston 3. By screwing the punch-bearing spindle more orless into the piston, it is possible to set the punch in the verticaldirection. Punch bearing spindle 11 is held in rotation by a springcatch 12 which goes into a groove in the punch-bearing spindle.

Piston 3 is held in rotation by a linchpin 13, keyed into the piston,which penetrates into an appropriate housing 14 of the punching machinebody. During its penetration into this housing, linchpin 13 actuates twopush rods 15 and 16 of a micro-contact that controls the drivinghydraulic fluid distributor.

Punch 17 is fixed to punch-bearing spindle 11 through sleeve 18. Thissleeve is surrounded by separating unit 19 which consists of aperforated frame that has a lower part bearing on the part to be punchedand an upper part surrounding the punch-bearing spindle and the sleevewhich holds the punch to the punch-bearing spindle. A part 20 bearing alinchpin 21 can slide into a hole 22 inside the punch bearing spindleand this linchpin bears against the upper edge 23 of separating unit 19.Part 20 is pushed with respect to the piston by a spring 24.

Operation is as follows:

When the piston moves downwards, pressed by the under pressure liquidthat feeds chamber 4, linchpin 21 is pressed on the edge 23 of theseparating unit. At the end of a certain stroke, the lower part ofseparating unit 19 presses on the part to be punched, spring 24 beginsto compress and the punch continuing its downward motion punches thepart. The pressure and the energy absorbed in chamber 5 compensate forthe elastic energy of the driving hydraulic fluid at the time ofthroughout punching. At the end of the stroke, the application of thedriving fluid ceases and the piston is reset under the influence of thedamping hydraulic fluid pressure and of spring 24 which tends to bringback the punch upwards by pressing on the separating unit, which thusmaintains the plate into place during extraction of the punch.

FIG. 3 shows the punching machine control circuit. The oil underintermediate pressure to be used in damping and in resetting thepunching machine, comes from an oleo-pneumatic accumulator 26 under apressure of 700 p.s.i. and reaches the punching machine through pipe 7,junction 8, hole 9, and restricted passage 10. The oil to be used forcontrol comes from a pump 27 and passes through a three-way andtwo-position distributor 28, controlled by the microcontact whosepush-rods 15 and 16 were mentioned in the description of FIG. 1, and bypipe 6. It can be seen that as the pressure in the lower chamber of thepiston is maintained on a permanent basis, a four-way and three-positiondistributor of the type usually used with hydraulic jacks is notnecessary.

In the punching machine example that has just been described, it hasbeen supposed that the damping hydraulic pressure was 700 p.s.i. for adriving hydraulic fluid pressure of 3,500 p.s.i., that is, takingaccount the ratio of the cross-sections of chambers 4 and 5, a stressratio on either side of the piston of 0.10. In fact, a ratio rangingbetween 0.05 and 0.30 may be adequate.

What I claim is:

1. A hydraulic punching machine for punching metal sheets in whichknocks and shocks produced by punching are automatically eliminatedcomprising a body, a chamber in said body, a piston adapted toreciprocate in said chamber, a punch, means for securing said punch tosaid piston, a first source of high pressure hydraulic fluid feedingsaid chamber and actuating said piston by its upper face, a secondsource of damping hydraulic fluid which permanently feeds said fluidinto said chamber at a pressure lower than said high pressure and whichactuates said piston at its lower face, said chamber having a smallopening through which said lower pressure damping fluid enters, and thesection of said opening being dimensioned to provide a pressure loss atsaid upper face and said lower face of said piston respectively which isequal to the difference between said high damping pressure and saidlower damping pressure.

2. A hydraulic punching machine for punching metal sheets in whichknocks and shocks produced by punching are automatically eliminatedcomprising a body, a chamber in said body, a piston adapted toreciprocate in said chamber, a punch, means for securing said punch tosaid piston, a separating unit surrounding said punch and adapted toseparate the punch from the sheet to be punched after punching, meansfor controlling said separating unit, a first source of high pressurehydraulic fluid feeding said chamber and actuating said piston at itsupper face, a second source of damping hydraulic fluid which permanentlyfeeds said fluid into said chamber at a pressure lower than said highpressure and which actu- References Cited UNITED STATES PATENTS2,857,157 10/1958 Bonquet 83-615 X 2,039,847 5/1936 Howland-Shearman83140X 2,612,951 10/1952 Palmleaf 83-639 X FOREIGN PATENTS 869,526 5/1961 Great Britain.

ANDREW R. JUHASZ, Primary Examiner US. Cl. X.R. 83-615, 639, 640

